photoEating fast food with a high fat content is never healthy, but having a cup of coffee along with it is even worse, according to researching writing in the Journal of Nutrition.

But why would coffee be unhealthy? After all, it has no fat and no calories, if you drink it black. That’s not the point, say researchers from the University of Geulph, in Ontario, Canada.

The unhealthy part is the caffeine, and what that does when it interacts with the fat. Even a healthy person’s blood sugar levels jump after eating a high-fat meal. But the levels are nearly off the chart when caffeinated coffee is added to the mix. (Read consumer complaints about fast food chains).

Can’t clear blood sugars

"The results tell us that saturated fat interferes with the body's ability to clear sugars from the blood and, when combined with caffeinated coffee, the impact can be even worse," said Marie-Soleil Beaudoin, a PhD student who conducted the study with U of G professors Lindsay Robinson and Terry Graham. "Having sugar remain in our blood for long periods is unhealthy because it can take a toll on our body's organs."

The study on a select group of healthy men found that drinking a high-fat cocktail spiked blood sugar levels an average of 32 percent. But the results showed blood sugar levels increased by 65 per cent compared to what they were when participants had not ingested the fat and caffeinated coffee.

An hour or two apart can be a problem

Not only that, the fat and the coffee didn’t necessarily have to be consumed at the same time. Researchers noticed the increase in blood sugar levels when the meal and the coffee were consumed an hour or two later.

"This shows that the effects of a high-fat meal can last for hours," said Beaudoin. "What you eat for lunch can impact how your body responds to food later in the day."

Typically when we ingest sugar, the body produces insulin, which takes the sugar out of the blood and distributes it to our muscles. But the researchers found that the fatty meal affected the body's ability to clear the sugar out of the blood.

The researchers say they believe the combination of fat and caffeine disrupts the communication between the gut and the pancreas, which could be playing a role in why participants couldn't clear the sugar from their blood as easily. Beaudoin says the results of the study are particularly important for people at risk for metabolic diseases and Type 2 diabetes.

Limit caffeine

"We have known for many years that people with or at risk of Type 2 diabetes should limit their caffeine intake,” she said. “Drinking decaffeinated coffee instead of caffeinated is one way to improve one's glucose tolerance.”

And it goes without saying, it’s best to avoid foods high in fat, especially if you are at risk for Type 2 diabetes.